From PCWorld:

On Tuesday, Microsoft outlined the Windows 10 versions you’ll know, love and buy when the new operating system launches this summer. But the company withheld key details, such as how it will eventually make money on it.

As with Windows 7, 8, and now 10, Windows 10 will be sold in two versions for consumers: Windows 10 Pro, and Windows 10 Home. The Windows Phone brand, as Microsoft has indicated previously, is going away: It will be renamed Windows 10 Mobile, and will ship on phones and small tablets. Businesses and enterprises will also receive their own versions: Windows 10 Enterprise, Windows 10 Mobile Enterprise and Windows 10 Education.

And yes, Windows 10 will be a free upgrade—at least for consumers: “As we announced earlier this year, for the first time ever, we are offering the full versions of Windows 10 Home, Windows 10 Mobile and Windows 10 Pro as a free and easy upgrade for qualifying Windows 7, Windows 8.1 and Windows Phone 8.1 devices that upgrade in the first year after launch,” Microsoft’s Tony Prophet, the company’s corporate vice president of Windows and search, wrote in a blog post “Once you upgrade, you have Windows 10 for free on that device.”

Microsoft has said previously that Windows 10 beta testers, known as Insiders, will receive a free upgrade to the so-called “RTM” version of the software, the same version that will be shipped to stores and to hardware makers. Windows 7, Windows 8.1 and Windows Phone 8.1 users will be able to upgrade for free, as long as they do it within the first year that the OS ships,

Microsoft did not say, however, what Windows 10’s eventual price would be, nor did the company say whether it would be offered on a subscription model (or what that subscription cost would be).

There’s one hoop to jump through on the path to Windows 10: According to Prophet’s blog post, Windows 8 users will need to upgrade to Windows 8.1 before upgrading to Windows 10. That’s a small hitch for consumers, although businesses who carefully upgrade software for fear of breaking their proprietary applications may need to take care.

Microsoft also hasn’t said which versions of Windows 7 will upgrade to Windows 10. A Microsoft spokeswoman said in an email that she couldn’t comment beyond Prophet’s blog post.

Still, Microsoft has been far more transparent than ever before about what to expect as consumers and businesses upgrade to Windows 10. Because the upgrade will be a free one, pricing issues aren’t critical—yet. Eventually, however, Microsoft’s going to have to answer the one question on everyone’s mind: how exactly it plans to make money off Windows 10.